Discrepancy of universe's size and age

Discussion in 'Astronomy, Exobiology, & Cosmology' started by simple-mind, Mar 15, 2013.

  1. simple-mind Registered Member

    Messages:
    7
    Stumbling over some basic numbers of the universe's current standard model: 13.75 billion years old, 78 billion light years diameter. How can this be? If it has been expanding with light speed since big bang, I would expect a diameter not bigger than 27.5 billion light years.

    What's the reason for this 'discrepancy'?
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. origin Heading towards oblivion Valued Senior Member

    Messages:
    11,888
    The universe is not expanding at light speed.

    Remember the universe is expanding all the time and the light emitted 13.7 billion years ago was from a source that was much closer to us than it is now. The light that we are seeing from the source is 13.7 years old and we have been moving apart since that time. So the distance 'now' to that source is much more than 13.7 billion ly.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. arauca Banned Banned

    Messages:
    4,564



    Is the Big Bang really 13.8 b old ?

    "We have found that this is the oldest known star with a well-determined age," said Howard Bond of Pennsylvania State University in University Park, Pa., and the Space Telescope Science Institute in Baltimore, Md. The star could be as old as 14.5 billion years (plus or minus 0.8 billion years), which at first glance would make it older than the universe's calculated age of about 13.8 billion years, an obvious dilemma. But earlier estimates from observations dating back to 2000 placed the star as old as 16 billion years. And this age range presented a potential dilemma for cosmologists. "Maybe the cosmology is wrong, stellar physics is wrong, or the star's distance is wrong," Bond said. "So we set out to refine the distance." The new Hubble age estimates reduce the range of measurement uncertainty, so that the star's age overlaps with the universe's age—as independently determined by the rate of expansion of space, an analysis of the microwave background from the big bang, and measurements of radioactive decay.

    Read more at: http://phys.org/news/2013-03-hubble-...-star.html#jCp
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. Tamorph Registered Member

    Messages:
    16
    You have to differentiate between the universe we can see and the universe as a whole.

    By definition, the universe we can 'see' is expanding at the speed of light. The 'edge' of the universe, that we can't 'see' is much further away.

    It is generally accepted that at the big bang the universe expanded 'faster than the speed of light, and that it is still expanding faster than the speed of light today.

    In his book 'Just Six Numbers: The Deep Forces that Shape the Universe' Cosmologist and Astrophysicist Sir Martin John Rees believes that the number of light years to the edge of the current universe would need to be written not ‘with ten zeros, not even with a hundred, but with millions’.
     
  8. simple-mind Registered Member

    Messages:
    7
    Ok, we have to make clear from which inertial frame of reference we are talking when we say 'age' and 'size'. For these considerations I suggest to use a virtual observer at the center of the universe. From this point of view the radius of the universe should not be bigger than age x c, c being the speed of light, unless the expansion took place with a speed greater than the speed of light. Agreed? So I could imagine the following possibilities:

    (a) Expansion took place with a speed greater than the speed of light. If true, how does this relate to Einstein's theory of relativity, which supposes the speed of light being the upper limit for movement of matter?

    (b) The age of 13.75 billion years and size of 78 billion ly relate to a different inertial frame of reference. If true, which one would that be, and which age and size would result if transformed to the inertial frame of reference being the center of the universe?
     
  9. Tamorph Registered Member

    Messages:
    16
    According to Dr Kristine Spekkens, a Jansky Fellow based at Rutgers University, the answer is as follows:

    According to Dr Philip Gibbs of the University of California, Riverside, the answer is as follows:

    Or, to put it my way!

    The expansion happened faster than the speed of light because the universe is mostly vacuum. It was the vacuum that was expanding.
     

Share This Page